The present invention relates to a method for manufacturing a semiconductor device, and in particular, a manufacturing method using a metallic silicide in forming transistors, wiring layers and contact holes.
Recently there has been adopted a method wherein a metallic silicide is used in forming transistors, wiring layers and contact holes, to greatly reduce resistance and attain faster operation. The conventional manufacturing method will be described below with reference to FIGS. 1a-1c which shows a vertical section of elements process by process.
At the surface of a p-type semiconductor substrate 1, a field oxide film 2 is formed between in a region II for forming a MOS transistor and a region III for contact with the semiconductor substrate 1, or in a wiring region I, and thereafter an oxide film is formed throughout the whole. The portion of the oxide film corresponding to the region III for contact with the substrate is removed by wet etching, and the oxide film remains as a gate oxide film 3 on the surface of the MOS transistor forming region II. A polycrystalline silicon film 4 and a metallic silicide film 5 are formed successively on the whole surface, and then resist is applied onto the surface of the metallic silicide film 5 to form patterned resist films 6a, 6b and 6c (FIG. 1a).
Etching is performed with the resist films 6a, 6b and 6c as masks, and the polycrystalline silicon film 4. The metallic silicide film 5 is patterned as shown in FIG. 1b, whereby polycrystalline silicon films 4a, 4b, 4c and metallic silicide films 5a, 5b, 5c are formed in the wiring region I, MOS transistor region II and substrate contact region III.
Oxide films 7 are formed to cover the thus-formed polycrystalline silicon films 4a, 4b, 4c and metallic silicide films 5a, 5b, 5c (FIG. 3c). Thereafter, a wiring layer, a MOS transistor and a contact hole are formed, although these are not shown.
When the oxide films 7 are formed in the conventional method, however, the interfaces of the polycrystalline silicon films 4a, 4b, 4c and the metallic silicide films 5a, 5b, 5c are exposed to an oxidizing atmosphere, thereby causing bird's beaks 8. Once the bird's beaks 8 are formed, the polycrystalline silicon films and the metallic silicide films are separated from each other, deteriorating the production yield and reliability.